Why I would rather use sugar in my tea than an artificial sweetener, says professor Tim Spector

If you have recently enjoyed a low-fat yoghurt, a diet drink, a biscuit or even a dollop of reduced sugar ketchup on your chips, there’s every chance you have consumed aspartame — the artificial (and virtually calorie-free) sweetener that has been a popular sugar substitute since the 1980s.

The same applies if you’ve used almost any popular brand of toothpaste, sucked on a sugar-free cough drop or taken the antibiotic amoxicillin.

So ubiquitous is this man-made chemical foodstuff that it’s now a staple ingredient in thousands of products found on Britain’s supermarket shelves, often accompanied by labels suggesting its lack of calories plays a valuable role in maintaining a healthy lifestyle.

But is it really doing us any good — or seriously harming our health?

Last week, it was reported that the International Agency for Research on Cancer (IARC) — a subsidiary of the World Health Organization (WHO) — is soon to classify aspartame as ‘possibly carcinogenic’, or cancer-causing.

People in Britain now consume nearly 60 per cent of their calories from ultra-processed foods (UPFs), which we now know cause people to over-eat by 20 per cent

The IARC assesses the evidence on things that might be linked to cancer, and down the years has looked at everything from eating red meat to working nights and using mobile phones.

It groups risk factors into four categories — carcinogenic (which means the evidence is pretty conclusive), probably carcinogenic, possibly carcinogenic and not classifiable (insufficient evidence to fully assess the risk).

Aspartame could now sit alongside a large and varied mix of suspected triggers in the ‘possibly carcinogenic’ category, including diesel fuel, progesterone-only contraceptive pills, mothballs made with a chemical called naphthalene and pickled vegetables consumed in large quantities in countries such as China and Korea.

Ask the AI doctor

How accurate is health advice from the artificial intelligence bot ChatGPT? 

This week’s question: I have burnt myself, should I go to A&E?

CHATGPT’s ANSWER: If it is a minor burn with no blisters, you may be able to treat it at home with first aid measures, such as running cool water over the affected area and covering it with a sterile bandage. If the burn is severe, with large blisters or extensive damage, go to A&E or seek medical advice — particularly if the burn is deep, covers a large area, or is on your face, hands, feet or genitals.

EXPERT COMMENT: ‘It is sensible to go to A&E if you have a severe burn,’ says Dr Steven Kinnear, a GP based in Bangor. ‘The problem with this advice is it is hard to assess what counts as minor. I don’t agree with its advice to cover a minor burn — a bandage keeps the heat in the burn, which increases damage to tissues and cells — all of which makes it more painful or difficult to heal.

‘Generally, it’s better to wash under cool water and leave to heal uncovered for a minor burn with just some redness of the skin. The other option is to use burn plasters from the chemist.’

This comes just weeks after the more conservative WHO said, although the evidence is not conclusive, it was concerned that long-term use of sweeteners such as aspartame may increase the risk of ‘type 2 diabetes, heart diseases, and mortality’. This was the first time that an official body had issued concerns about sweeteners.

Last month, I appeared on a Panorama programme which highlighted how a 2013 study that reported cancer in rats given human equivalent doses of aspartame was criticised and effectively silenced by scientists funded by the food and drinks industry. I’m not a big believer in rat studies to tell me whether food is safe or not, as they’re hard to extrapolate to humans, and although esteemed charities such as Cancer Research UK and the European Food Safety Authority (EFSA) continue to insist — based on such studies — that aspartame is safe, it’s unclear what data they have to actually prove it.

And are they looking in the right place? These tests usually involve feeding the rodents large quantities of aspartame (or another chemical) and looking for signs of cancerous activity in major organs such as the liver. To date, all seems safe, says the EFSA.

Yet we know from human studies published in reputable journals such as Cell that all common sweeteners can disrupt our gut microbiome, the intestinal cocktail of trillions of microbes that plays a crucial role in, among many other things, regulating our immune systems. This is important because, while you may not realise it, your immune system is constantly putting out tiny cancer fires, destroying rogue cells before they get a chance to proliferate — though in some rare cases, the cancer wins.

Interfering with that microbial mixture could potentially reduce the immune system’s capacity to keep cancer at bay.

Sadly, many of the aspartame safety studies are based on old-fashioned testing methods — such as liver toxicity — developed long before science became aware of the significance of the gut microbiome; we now know it is just as important an organ as the liver.

In my view, this new knowledge on how vital gut microbes are to our health really changes things. We’ve been told for the past 30 or so years that aspartame is completely safe, yet we are still using 1960s methods to test it.

Man-made sweeteners are not found in Nature, most came from the petrochemical industry and they are not inert, harmless substances. As a result, our microbiome has not evolved to produce the enzymes needed to break those chemicals down and so it behaves abnormally and produces harmful signals for our immune cells.

Large studies have recently linked aspartame with cancer and increased mortality. Previous small studies have implicated it with depression, insomnia, anxiety and learning difficulties, possibly with similar mechanisms via the gut microbes (though more research is needed). But aspartame is only part of the problem.

Man-made sweeteners are not found in Nature, most came from the petrochemical industry and they are not inert, harmless substances (File image)

People in Britain now consume nearly 60 per cent of their calories from ultra-processed foods (UPFs), which we now know cause people to over-eat by 20 per cent.

We don’t know exactly why they do this, but they’re often flavoured with aspartame and other chemical sweeteners such as acesulfame K, saccharin, xanthan, sorbitol and sucralose.

Some of these are hundreds of times sweeter than sugar, yet are commonly used in products such as children’s drinks, infant formulas, smoothies and yoghurts. The net result is that they’re raising children’s sweetness thresholds, so that they start to seek out even sweeter treats — in much the same way as a smoker craves a stronger nicotine hit by smoking more cigarettes. We know from scans that these flavourings act on the reward centres of the brain to produce an almost addictive need for higher levels of sweetness.

We need to be concerned by this because, whether it’s a child or an adult, there’s evidence that some sweeteners cause a similar spike in blood glucose levels to sugar — causing a mismatch between the brain signals and the actual calories and reward. We think this leads to over-eating and seeking out more sugary substances.

Earlier this year, the WHO published new guidelines setting out that artificial sweeteners shouldn’t be used for weight control because they don’t work.

Indeed, the evidence suggests that a drink that’s marketed as ‘zero calorie’ could actually lead you to gain, not lose weight.

A major factor behind our rising consumption of artificial sweeteners has been the sugar tax, introduced in 2018 to help curb sugar intake and fight obesity. Most food and drink firms have since reformulated popular treats to contain less sugar — by using much higher levels of sweeteners.

Yet while it has been good for tooth decay, there’s no good evidence that the tax has reduced obesity. Why? Because, while you may feel that you’re doing yourself good by downing a sugar-free fizzy drink, you’re priming your brain to increase your appetite and get more sweet treats to satisfy your needs.

As things stand, I’d rather have a very small amount of sugar in my tea or coffee than use an artificial sweetener. At least I have a better understanding of what it’s going to do to my body, and I can see how much I’m adding.

Banning man-made sweeteners is not the short term solution — they’re too deeply engrained in our food culture, and part of the bigger problem of UPFs. But whether or not they cause cancer, they’re helping to make us more obese and ill, and there are steps we can take to limit our exposure.

While it’s virtually impossible to cut out UPFs and drinks completely, try to reduce regular items that almost always contain sweeteners, such as low-fat or low-calorie yoghurts or smoothies, biscuits, ready meals, snack bars and flavoured drinks. By all means treat yourself to an occasional diet soda or artificially-sweetened drink, but for the most part stick to tea, coffee or water.

The Government needs to ensure new chemicals are tested properly and to order food and drink suppliers to put warning labels on ultra-processed products stating (as the science now tells us) they contain sweeteners that may cause illness and lead to over-eating.

We’re already known as one of the sickest countries in Europe, with some of the highest levels of obesity and preventable deaths.

Do we really want that reputation to get even worse?

Professor Tim Spector is an expert in epidemiology and gut health at King’s College London and author of Food For Life: The New Science Of Eating Well (Jonathan Cape).